In general, a tire is one of the components constituting a vehicle. The tire directly contacts a road surface. Air in the tire absorbs shocks like a spring. Specifically, the air in the tire absorbs shocks generated due to irregularity of the road surface to improve comfort in driving of the vehicle.
The tire includes a tread, which is a rubber layer that contacts the road surface, a sidewall connected to the tread, the sidewall constituting a side surface of the tire, a bead connected to the sidewall, the bead being fixed to a rim of each wheel of the vehicle, a carcass mounted in the tire, the carcass forming a framework of the tire and exhibiting high fatigue resistance to bending and stretching of the sidewall, and a belt disposed between the tread and the carcass for protecting the carcass and improving the rigidity of the surface of the tread. The tread includes a block and a groove. A kerf is formed in the block. The rigidity of the block is appropriately adjusted by the kerf so as to satisfy the requirements of the tire.
A snow tire is a tire manufactured to have better braking, steering, and traction performance than a general tire while traveling on a snowy road or an icy road in the winter. While traveling on a snowy road or an icy road, grip force is maintained in driving, braking, and cornering due to the edge effect of the kerf.
In a general snow tire, sub blocks constituting a block are separated from each other by a tread kerf formed in each sub block. As a result, the interconnection between the sub blocks is lost, whereby rigidity of the block is lowered. That is, interconnection between the sub blocks is lost in a direction normal to a center line of the kerf, whereby the rigidity of the block is lowered. During the movement of the tire, therefore, the sub blocks of the tread partitioned by the kerf excessively fall, and a leading portion of the tire is rolled. As a result, frictional force between the tire and the road surface is reduced. Consequently, the performance of the tire is lowered when driving, braking, and cornering on a dry road and a wet road. In addition, the wear resistance of the tire is lowered.
Three-dimensional kerfs that maintain the rigidity of a tread block based on interconnection between the sub blocks achieved by the kerf in a direction normal to the surface of a tire are disclosed in Korean Registered Patent No. 10-0913597 and Japanese Patent Application Publication No. 2011-991. However, the conventional three-dimensional kerfs do not exhibit desired rigidity. For this reason, there is a high necessity for a new type of three-dimensional kerf.
FIG. 7 is a perspective view schematically showing a block having a conventional three-dimensional kerf formed therein. As shown, a block 10 is provided at the middle of a top surface 11 thereof with a zigzag wave-shaped three-dimensional kerf 12, which is formed in a depth direction (a z-axial direction) of the block 10 to divide the block 10 into sub blocks 10a and 10b. When force is applied to the three-dimensional kerf 12 in directions indicated by arrows A during traveling on a tire, as shown in FIG. 7, the rigidities of the sub blocks differ from each other due to the three-dimensional kerf 12 in a direction in which the tire moves as shown in FIG. 8. As a result, the effect of interlocking between the sub blocks is low, and locking force is concentrated at one or two points (the interlocking force is indicated by arrows B).